Polyether polyol or copolymerized polyether polyol is a long chain polyol having hydroxyl terminal groups, and may be used for the soft segment of thermoplastic polyester resins and polyurethane (PU) elastomer and raw material of elastic fibers (Spandex) , synthetic leathers ,etc.
The method for preparing polyether polyol or copolymerized polyether polyol essentially uses one or more cyclic ethers to carry out the ring-opening polymerization or ring-opening copolymerization. This process needs a proton acid having strong acidity, such as perchloric acid, fluorosulfonic acid and the like, or a Lewis acid, such as boron chloride, aluminum chloride, antimony pentachloride and the like, as a catalyst; sometimes the process even needs an activator, such as carboxylic anhydride and the like.
The polyether polyol which has been produced and used for Spandex fibers in the industry primarily introduces polytetramethylene ether glycol ( hereinafter abbreviated as PTMEG). This reaction was first reported by Meerwein et al. (Angew. Chem. 72, 927 ( 1960) ) 3 PTMEG can be produced by polymerization of tetrahydrofuran (hereinafter abbreviated as ITHF) But because PTMEG is easy to crystallize at low temperatures and results in poor physical properties, the physical properties at low temperatures may be improved by adding other cyclic ether comonomers, such as propylene oxide.
U.S. Pat. No. 3,712,930 has disclosed a method for preparing polyether polyol in the presence of fuming sulfuric acid as a catalyst, but this method produces only products of molecular weight lower than 1000. In addition, U.S. Pat. No. 2,751,419, U.S. Pat. No. 5,393,866, and JP 52-32799 have disclosed methods of using fluorosulfonic acid as a catalyst, but these methods need hydrolysis after the reaction to obtain polyether polyol. However, fluorine-contained catalysts may yield fluorine-contained by-products which is difficult to separate Also fluorosulfonic acid reacts with water to produce hydrofluoric acid and sulfuric acid, the expensive fluorosulfonic acid is consumed in this process so that this process is at a disadvantage in cost of preparation. Furthermore, another disadvantage of this process is that hydrofluoric acid and sulfuric acid must be treated so that the use of expensive anti-corrosive equipment is necessary, such as glass lining equipment which subjects to instrumental scale-up limitation, and the productive efficiency of the equipment can not be increased so that there is a high investment in equipment. Also, because a large amount of waste water is produced, the subsequent waste water treatment process further increases manufacturing cost.
U.S. Pat. No. 5,149,862 has disclosed a method for using ZrO.sub.2 /SO.sub.4.sup.2 - as a catalyst, but the polymerization rate is so slow( the conversion in 19 hours is only 6% )that acetic acid/ acetic anhydride must be used to accelerate the reaction. U.S. Pat. No. 4,120,903 has disclosed a method of using Nafion.RTM. resin as a catalyst, but the resin is not easily prepared and lacks long-term stability and reactivity. In addition, EP-A-286454 has disclosed a method of using a Lewis acid or a proton acid as a catalyst; for example, antimony pentafluoride, silver tetrafluoroborate or trifluoromethanesulfonic acid can all be used as catalysts. Because the acidity of these catalysts is very strong, and use of special anti-corrosive equipment makes the process uneconomical.
Moreover, there have been various methods of preparing polyether polyol or copolymerized polyether polyol; for example, perchloric acid-acetic anhydride system is used in JP 45-13940; sulfuric acid-acetic anhydride system is used in JP 52-32680; fluorosulfonic acid-acetic anhydride system is used in JP 54-3718; and fluorinated sulfonic resin, Nafion.RTM., -acetic anhydride system is used in U.S. Pat. No. 4,153,786 Also, Lewis acid and an activator system have been used as catalysts; for example, boron fluoride-acetic anhydride system has been used in WP 52-32797; and solid acids, such as ZrO.sub.2 /SO.sub.4.sup.2- ; -acetic acid/acetic anhydride system have been used in U.S. Pat. No. 5,149,862. The above-mentioned methods which have been disclosed are two-step reactions, that is, after the reaction in these catalyst systems, polyether polyol with ester groups is obtained instead of hydroxyl terminal groups. Thereafter polyether polyol is obtained through alcoholysis or transesterification, so that the process is more complicated and the cost is higher.
Furthermore, JP 63-30931, JP 63-30932, U.S. Pat. No. 4,568,775 and USP 4,658,065 have disclosed a method for preparing polyether polyol or copolymerized polyether polyol, which uses heteropoly acid as a catalyst. This is a one-step process, and directly obtains polyether polyol or copolymerized polyether polyol with hydroxyl terminal groups, but the number of water of hydration of heteropoly acid should be strictly controlled. Because heteropoly acid has a certain degree of solubility in the organic phase, heteropoly acid still remains in the product. If using a base for neutralization, the catalyst can not be reused. If water is used to extract heteropoly acid, polyether polyol or copolymerized polyether polyol is not easily stratified because it is easily emulsified by water, and separation can only be completed with difficulty. It is necessary to use hydrocarbon solvents, such as n-octane, to remove residual heteropoly acid and treat with an adsorbent, such as active carbon, as has been disclosed in EP 181621 to provide commercial products. Hence, a complicated treatment procedure for separation and purification is required with an expensive and difficult preparation process
According to the above, it is understood that defects are present in each of the existing processes which call for improvement. In order to solve the above-mentioned problems, the inventors of the present invention extensively studied heteropoly acidic catalysts, and found that if using catalysts synthesized from heteropoly acidic salts and oxides and/or binders, the target product polyether polyol or copolymerized polyether polyol will be directly produced. In this way, the present invention is achieved.
According to the present invention, it is an advantage that the corrosion of catalysts is low, the catalyst may be separated from the organic phase. Thus it is only necessary to distill off solvent and unreacted monomer in the organic phase to obtain a polyether polyol or copolymerized polyether polyol with hydroxyl terminal groups. Furthermore, without using any other promoter, the unreacted monomer may be recycled to the process for reuse.
Moreover, because the catalysts of the present invention have low solubility in the organic phase, there are no problems of any remaining heteropoly acidic salts in the product, so a complicated procedure for treating the solvent during the preparation process is not necessary. Furthermore, after reaction, it is only necessary to separate the catalysts by filtration or centrifigation. If the catalysts of the present invention are used as the catalyst of the fixed bed reactor, complicated separation procedures for catalysts and products may be avoided, and it is only necessary to distill off unreacted monomer to directly obtain polyether polyol or copolymerized polyether polyol without filtration Without using any other promoter, such as carboxylic anhydride, the unreacted monomer may be recycled to the preparation process for reuse through reduced distillation so that the process is simpler. According to the present invention, the molecular weight of products ranges from 500 to 3000, which is suitable for use as raw material of polyurethane elastomer, synthetic leathers, elastic fibers, etc. The merits of the present invention are a simple preparation process, a small amount of waste water, a low investment in equipment, and an inexpensive cost of preparation.